JP4206793B2 - Variable valve operating device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a variable valve operating apparatus for an internal combustion engine in which variable valve mechanisms that are operated by hydraulic pressure are provided on both an intake side and an exhaust side.
[0002]
[Prior art]
In order to improve the output and fuel efficiency of an internal combustion engine, various variable valve mechanisms that can change the valve lift characteristics of intake and exhaust valves have been proposed. For example, Patent Document 1 discloses a variable valve mechanism that uses both a hydraulic actuator and an electric actuator.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-161721
[Problems to be solved by the invention]
When variable valve mechanisms that change the valve lift characteristics by operating hydraulic pressure from a hydraulic pressure source such as an oil pump are provided on both the intake side and the exhaust side, there are the following problems. In a situation where the hydraulic pressure is low (the oil temperature is high), in order to ensure the operational responsiveness of both variable valve mechanisms, the oil pump has a large capacity and large size, which increases costs and equipment. I will invite you. Alternatively, if at least one of the variable valve mechanisms is electrically operated, the cost is also increased, and the power consumption is increased, so that the variable valve mechanism can sufficiently obtain the fuel consumption improvement effect that is the original purpose. Can not.
[0005]
The present invention has been made in view of such a problem, and a variable valve for an internal combustion engine in which a variable valve mechanism that operates by hydraulic pressure to change valve lift characteristics is applied to each of an intake side and an exhaust side. Reduces cost and fuel consumption by reducing the size and capacity of hydraulic sources such as oil pumps while avoiding the fact that the operating responsiveness of the variable valve mechanism cannot be ensured due to a decrease in hydraulic pressure or an increase in oil temperature. The main object of the present invention is to provide a novel variable valve operating apparatus for an internal combustion engine that can be improved.
[0006]
[Means for Solving the Problems]
A variable valve mechanism is provided on each of the intake valve side and the exhaust valve side, which is actuated by hydraulic pressure from a hydraulic pressure source to change the valve lift characteristics. A hydraulic parameter related to the hydraulic pressure is detected, and based on this hydraulic parameter, the operation of only one of the intake side variable valve mechanism and the exhaust side variable valve mechanism is prohibited, and the remaining other Operates only the variable valve mechanism .
[0007]
【The invention's effect】
According to the present invention, since the operation of only one of the variable valve mechanisms is prohibited based on the hydraulic parameter, the variable valve mechanism can be achieved without increasing the size and capacity of a hydraulic source such as an oil pump. It can be avoided that the operation responsiveness of the is inadvertently lowered. Therefore, it is possible to reduce the size and capacity of the hydraulic power source without reducing the fail-safe property, thereby reducing the cost and improving the fuel consumption.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG. 1, an intake side variable valve timing mechanism (hereinafter referred to as intake VTC) 13 as an intake side variable valve mechanism can continuously change the valve timing of the intake valve. An exhaust side variable valve timing mechanism (hereinafter referred to as an exhaust VTC) 15 as a valve mechanism can continuously change the valve timing of the exhaust valve. These VTCs (valve timing controls) themselves are known as disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 2002-161721, and only a brief description will be given here.
[0009]
Each VTC includes a housing 43 fixed to a cam sprocket 47 that rotates in conjunction with a crankshaft, and a vane 44 that is housed in the housing 43 and fixed to the intake camshaft 14 or the exhaust camshaft 16. have. Between the vane 44 and the housing 43, two hydraulic chambers 45 and 46 connected to the two VTC oil supply passages 34 or 35 (34a and 34b on the intake side; 35a and 35b on the exhaust side) are liquid-tight. Is defined. In accordance with the hydraulic pressure supplied to these hydraulic chambers 45, 46, the vane 44 rotates relative to the housing 43, the phase of the camshafts 14, 16 with respect to the phase of the crankshaft changes, and the operating angle of the intake / exhaust valves Changes to the advance side or the retard side.
[0010]
The engine control unit 1 is a well-known digital computer having a CPU, ROM, RAM, and an input / output interface, and stores and executes various control processes as described later. That is, the engine control unit 1 is a vehicle that uses a water temperature signal 2, an intake air amount signal 3, a throttle sensor signal 4, an oxygen sensor signal 5, an engine rotation signal 6, an intake cam angle sensor signal 19, an exhaust cam angle sensor signal 20, and the like. Control signals are output to various actuators based on various detection signals representing the operating state, and in particular, commands are respectively given to the intake VTC solenoid 11 as the intake side hydraulic control valve and the exhaust VTC solenoid 12 as the exhaust side hydraulic control valve. An intake VTC control signal 9 and an exhaust VTC control signal 10 are output as values (energization amount). The VTC solenoids 11 and 12 control the supply hydraulic pressure to the hydraulic chambers 45 and 46 by controlling the connection status and opening degree of the VTC oil supply passages 34 and 35 according to the command value.
[0011]
2 and 6 schematically show the hydraulic circuits of the VTCs 13 and 15. The cylinder block 41 is provided with an oil pump 31 as a hydraulic pressure source. The hydraulic oil (lubricant / engine oil) pressurized by the oil pump 31 passes through the block main gallery 32, the VTC solenoid oil supply passage 33, the VTC solenoids 11 and 12 and the VTC oil supply passages 34 and 35 described above, and the cylinder. It is supplied to VTCs 13 and 15 provided in the head 42.
[0012]
In the first, second, and fifth embodiments to be described later, as shown in FIG. 2, as a hydraulic parameter related to the hydraulic pressure, in the middle of the hydraulic pressure supply path from the oil pump 31 to the VTC solenoids 11 and 12, for example, in the block main gallery 32. An oil temperature sensor (hydraulic parameter detecting means) 24 for detecting the temperature of the hydraulic oil, that is, the oil temperature is provided. In the third, fourth, and sixth embodiments to be described later, as shown in FIG. 6, the hydraulic oil pressure, that is, the hydraulic pressure, is supplied to the VTC solenoid oil supply passage 33 in the middle of the hydraulic pressure supply route from the oil pump 31 to the VTC solenoids 11 and 12. A hydraulic sensor (hydraulic parameter detecting means) 22 for detecting the above is provided.
[0013]
3 to 5, 7, 7, 8, 10, and 11 are flowcharts showing the control process stored and executed by the engine control unit 1. Referring to FIG. 3, in S (step) 1, an intake VTC switching permission flag Vi and an exhaust VTC switching permission flag Ve are initialized to zero. In S2, based on the engine speed and the engine load, it is determined whether or not it is an operating region (ON region) in which the hydraulic pressure is supplied to at least one of the hydraulic chambers 45 and 46 of the intake VTC 13 to operate the intake VTC 13. If it is determined that the operation region is the intake VTC 13, the process proceeds to S <b> 3 and the intake VTC switching permission flag Vi is set to 1. If it is determined that it is not in the operating range of the intake VTC 13, S3 is bypassed and Vi remains at 0. Similarly, in S4, it is determined whether the operation region (ON region) in which the exhaust VTC 15 is operated by supplying hydraulic pressure to at least one of the hydraulic chambers 45, 46 of the exhaust VTC 15 mainly based on the engine speed and the engine load. judge. If it is determined that the exhaust VTC 13 is in the operating region, the process proceeds to S5, and the exhaust VTC switching permission flag Ve is set to 1. If it is determined that it is not in the operating range of the exhaust VTC 15, S5 is bypassed and Ve remains at 0.
[0014]
In S2 and S4 in FIG. 3, it is determined whether or not it is a region in which the hydraulic pressure is supplied to the VTC and the VTC is operated mainly by a request based on the engine speed and the engine load. The effect of the increase in pressure and the decrease in hydraulic pressure is not taken into consideration.
[0015]
FIG. 4 is a flowchart showing a flow of control according to the first embodiment as a reference example . In S11, the values of the intake VTC switching permission flag Vi and the exhaust VTC switching permission flag Ve set by the routine of FIG. 3 are read. In S12, it is determined whether or not the intake VTC switching permission flag Vi is 1. In S13, it is determined whether the exhaust VTC switching permission flag Ve is 1. If both Vi and Ve are determined to be 1, that is, the operation region of the intake VTC 13 and the operation region of the exhaust VTC 15, the processing after S 14 is performed. Exit.
[0016]
In S14, the output value Ot (oil temperature sensor signal 23 in FIG. 1) of the oil temperature sensor 24 shown in FIG. 2 is read. In S15, it is determined whether or not the output value (oil temperature) Ot is in a first high oil temperature state exceeding a predetermined first oil temperature threshold value Ot1 (for example, 120 to 130 ° C.). When it is determined that the first high oil temperature state is reached, the process proceeds to S16, where the value of the intake VTC switching permission flag Vi is set to 0 and the value of the exhaust VTC switching permission flag Ve is set to 0. That is, the operation of the intake VTC 13 is prohibited and the operation of the exhaust VTC 15 is prohibited.
[0017]
According to the first embodiment, in the first high oil temperature state in which the oil temperature is high and the hydraulic oil viscosity is lowered to lower the oil pressure, the operation of both the intake VTC 13 and the exhaust VTC 15, that is, the supply of the oil pressure is prohibited. is doing. Accordingly, in order to guarantee the operation responsiveness of the VTC, it is possible to avoid the VTC operation responsiveness from being inadvertently reduced without securing an excessively large capacity of the oil pump 31, and to reduce the size of the oil pump 31. By reducing the size and capacity, it is possible to reduce costs, reduce the size of the apparatus, reduce friction, and the like.
[0018]
FIG. 5 is a flowchart showing the flow of control according to the second embodiment of the present invention. The processing of S11 to S14 is the same as that of the first embodiment of FIG. In S15a, it is determined whether or not the output value (oil temperature) Ot of the oil temperature sensor 24 is in a second high oil temperature state that exceeds a predetermined second oil temperature threshold value Ot2. When it is determined that the second high oil temperature state is set, the process proceeds to S16a, and the value of the exhaust VTC switching permission flag Ve is set to zero. That is, only the operation of the exhaust VTC 15 is prohibited without prohibiting the operation of the intake VTC 13.
[0019]
The operation and effect according to the second embodiment will be described with reference to FIG.
[0020]
(1) For example, in the partial range, the intake valve opening timing IVO is advanced by the intake VTC 13 to increase the overlap from the IVO to the exhaust valve opening timing EVO, thereby increasing the internal EGR amount and improving fuel efficiency. Plan.
[0021]
{Circle around (2)} In a low speed region or the like, the intake valve closing timing IVC is advanced to bring the IVC closer to the bottom dead center, thereby increasing the actual compression ratio and improving the torque.
[0022]
(3) Because exhaust pulsation in the exhaust passage (exhaust pipe) causes exhaust to be exhausted more easily when exhaust pressure is low, in a fully open area, etc., retard the EVC to promote exhaust exhaust And improve output.
[0023]
Therefore, as in the second embodiment, in the second high oil temperature state (failure), the operation of only the exhaust VTC 15 is prohibited, so that the effects (1) and (2) due to the operation of the intake VTC 13 are achieved. As with the first embodiment, the oil pump 31 can be reduced in size and capacity while reducing costs and reducing friction.
[0024]
Since the operation of the exhaust VTC 15 is prohibited when the oil temperature is high, the output improvement effect (3) cannot be obtained. However, at such a high oil temperature, the necessity for improving the output is low and there is no practical problem.
[0025]
Referring to FIG. 9, (a) the case where the valve overlap is provided by advancing the intake VTC 13 and (b) the case where the valve overlap is provided by retarding the exhaust VTC 15 are compared. In (a), EGR is obtained mainly before top dead center, so it is easy to discharge EGR as the piston rises. In (b), EGR is obtained mainly after top dead center, so EGR is reduced as the piston descends. Easy to pull into the cylinder.
[0026]
In the VTC that operates by hydraulic pressure, there is a certain response delay from the signal input to the actual operation. For this reason, for example, if the state (b) is maintained during the transitional period when the sudden braking is performed from the operation region (b) or (b) to the state (c) such as the idle region, the EGR is placed in the cylinder. Since it is easy to draw in, combustion tends to become unstable. On the other hand, combustion is relatively stable in the state (a). Therefore, as in the second embodiment, by prohibiting the operation of only the exhaust VTC at high oil temperature, the valve overlap as in (b) is suppressed and avoided, and the combustion stability is improved. can do.
[0027]
Furthermore, by setting the second oil temperature threshold value Ot2 to be lower than the first oil temperature threshold value Ot1 of the first embodiment, the operating range of the VTC can be expanded and the drivability can be improved.
[0028]
FIG. 7 is a flowchart showing the flow of control according to the third embodiment as a reference example . The processes from S11 to S14 are the same as those in the first embodiment of FIG. In S15b, the output of the hydraulic sensor 22 shown in FIG. 6 (hydraulic sensor signal 21 in FIG. 1), that is, the hydraulic pressure Op is a first low hydraulic pressure state lower than a predetermined first hydraulic pressure threshold (for example, 100 to 150 Pa) Op1. Determine whether. When it is determined that the first low hydraulic pressure state is set, the process proceeds to S16b, and the value of the intake VTC switching permission flag Vi and the value of the exhaust VTC switching permission flag Ve are set to zero. As a result, the operation of intake VTC 13 is prohibited and the operation of exhaust VTC 15 is prohibited.
[0029]
The intake VTC and the exhaust VTC are operated by oil pressure, and when the oil pressure is low, the operation characteristics are deteriorated (responsiveness is delayed, etc.). Since the oil pressure decreases as the oil temperature increases, the oil pressure decreases as the viscosity decreases. Therefore, in the first and second embodiments described above, it is generally used in conventional engines as a substitute for oil pressure. The oil temperature of the oil temperature sensor is used as a parameter related to oil pressure to reduce the number of parts and cost. On the other hand, in the third embodiment, since the oil pressure is directly detected instead of the oil temperature which is a substitute characteristic, the control accuracy of the intake VTC and the exhaust VTC is excellent.
[0030]
FIG. 8 is a flowchart showing the flow of control according to the fourth embodiment of the present invention. The processing from S11 to S14 is the same as that of the first embodiment of FIG. In S15c, it is determined whether the output (hydraulic pressure) Op of the hydraulic pressure sensor 22 is in the second low hydraulic pressure state lower than the predetermined second hydraulic pressure threshold Op2. When it is determined that the second low hydraulic pressure state is set, the process proceeds to S16c, and only the value of the exhaust VTC switching permission flag Ve is set to 0 without changing the intake VTC switching permission flag Vi. Thereby, only the operation of the exhaust VTC 15 is prohibited without the operation of the intake VTC 13 being prohibited.
[0031]
According to such a 4th example, the main operation effects of the 2nd example and the 3rd example mentioned above can be obtained collectively. In other words, by prohibiting the operation of only the exhaust VTC, the operating range of the intake VTC related to the hydraulic pressure can be expanded to the limit, the operability is improved, and the combustion is stable compared to the case where the operation of only the intake VTC is prohibited. Improves. Further, since the hydraulic pressure can be detected directly, the control accuracy can be improved as in the third embodiment. Furthermore, by setting the second hydraulic pressure threshold value Op higher than the first hydraulic pressure threshold value Op1 of the third embodiment, the operating range of the VTC can be expanded and the drivability can be improved.
[0032]
FIG. 10 is a flowchart showing the flow of control according to the fifth embodiment of the present invention. The processing from S11 to S16a is the same as that of the second embodiment of FIG. That is, in the second high oil temperature state where the oil temperature Ot detected by the oil temperature sensor 24 is higher than the second oil temperature threshold value Ot2, the process proceeds from S15a to S16a, the exhaust VTC switching permission flag Ve is set to 0, and the operation of the exhaust VTC 15 is performed. Is prohibited. In subsequent S17, it is determined whether or not the oil temperature Ot is in a first high oil temperature state that exceeds a first oil temperature threshold value Ot1 (Ot1> Ot2) that is higher than the second oil temperature threshold value Ot2. If it is determined that the first high oil temperature state is reached, the process proceeds to S18, where the intake VTC switching permission flag Vi is set to 0, and the operation of the intake VTC 13 is prohibited.
[0033]
According to the fifth embodiment, in addition to substantially the same effect as the second embodiment, the operation prohibition of the exhaust VTC 15 and the operation prohibition of the intake VTC 13 are appropriately performed in this order as the oil temperature rises. Therefore, it is possible to ensure a sufficient VTC operating region and improve engine operability while reliably avoiding a failure state such as an inadvertent decrease in the operating response of the VTC.
[0034]
FIG. 11 is a flowchart showing the flow of control according to the sixth embodiment of the present invention. The processing from S11 to S16c is the same as that of the fourth embodiment of FIG. That is, in the second low hydraulic pressure state in which the hydraulic pressure Op detected by the hydraulic pressure sensor 22 is lower than the second hydraulic pressure threshold Op2, the process proceeds from S15c to S16c, and the exhaust VTC switching permission flag Ve is set to 0 to prohibit the operation of the exhaust VTC15. In subsequent S17a, it is determined whether or not the hydraulic pressure Op is in the first low hydraulic pressure state lower than the first hydraulic pressure threshold value Op1 (Op1 <Op2), which is a value lower than the second hydraulic pressure threshold value Op2. When it is determined that the first low hydraulic pressure state is set, the process proceeds to S18, where the intake VTC switching permission flag Vi is set to 0, and the operation of the intake VTC 13 is prohibited.
[0035]
According to the sixth embodiment, substantially the same effect as that of the fourth embodiment can be obtained, and the operation prohibition of the exhaust VTC 15 and the operation prohibition of the intake VTC 13 are performed step by step in this order as the hydraulic pressure decreases. Therefore, the VTC operating range can be expanded and the engine operability can be improved while reliably avoiding VTC failure (decrease in operating response).
[0036]
As described above, the present invention has been described based on specific embodiments, but the present invention is not limited to these embodiments, and includes various modifications and changes without departing from the spirit of the present invention. It is a waste. For example, in the above embodiment, a variable valve mechanism capable of continuously changing the valve lift characteristics is used. However, the present invention is not limited to this. Two positions for switching the valve lift characteristics in two stages according to the supply / stop of hydraulic pressure are used. A switching type variable valve mechanism may be used.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a variable valve operating apparatus for an internal combustion engine according to the present invention.
FIG. 2 is a hydraulic circuit diagram showing an example in which an oil temperature sensor is provided in the hydraulic circuit.
FIG. 3 is a flowchart showing a flow of a setting process for a switching permission flag.
FIG. 4 is a flowchart showing a control flow according to the first embodiment of the present invention.
FIG. 5 is a flowchart showing a control flow according to a second embodiment of the present invention.
FIG. 6 is a hydraulic circuit diagram showing an example in which a hydraulic sensor is provided in the hydraulic circuit.
FIG. 7 is a flowchart showing a control flow according to a third embodiment of the present invention.
FIG. 8 is a flowchart showing a control flow according to a fourth embodiment of the present invention.
FIG. 9 is an explanatory diagram for explaining the operation and effect when prohibiting only the operation of the exhaust VTC.
FIG. 10 is a flowchart showing a flow of control according to a fifth embodiment of the present invention.
FIG. 11 is a flowchart showing a control flow according to a sixth embodiment of the present invention.
[Explanation of symbols]
1 ... Engine control unit (operation prohibition means)
11. Intake VTC solenoid (intake side hydraulic control valve / operation prohibiting means)
13 ... Intake VTC (Intake side variable valve mechanism)
12. Exhaust VTC solenoid (exhaust side hydraulic control valve / operation prohibiting means)
15 ... Exhaust VTC (Exhaust side variable valve mechanism)
22 ... Hydraulic sensor (hydraulic parameter detecting means)
24. Oil temperature sensor (hydraulic parameter detecting means)
31 ... Oil pump (hydraulic power source)

Claims (9)

A hydraulic source for pressurizing the hydraulic oil;
An intake side variable valve mechanism that operates by hydraulic pressure to change the valve lift characteristics of the intake valve;
An exhaust side variable valve mechanism that operates by hydraulic pressure to change the valve lift characteristics of the exhaust valve;
Oil pressure parameter detecting means for detecting oil pressure parameters related to oil pressure;
Based on the oil pressure parameter detected by the oil pressure parameter detecting means, the operation of only one of the intake side variable valve mechanism and the exhaust side variable valve mechanism is prohibited, and the other variable action is left. An operation prohibiting means for operating only the valve mechanism;
A variable valve operating apparatus for an internal combustion engine. The hydraulic parameter detecting means variable valve device for an internal combustion engine according to claim 1 Ru oil temperature sensor der to detect the oil temperature.   The operation prohibiting means prohibits the operation of both the intake side variable valve mechanism and the exhaust side variable valve mechanism when the oil temperature detected by the oil temperature sensor exceeds a first oil temperature threshold. A variable valve operating apparatus for an internal combustion engine as described. The operation prohibiting means prohibits the operation of only one of the variable valve mechanisms when the oil temperature detected by the oil temperature sensor exceeds a second oil temperature threshold that is lower than the first oil temperature threshold. The variable valve operating apparatus for an internal combustion engine according to claim 3 . The hydraulic parameter detecting means variable valve device for an internal combustion engine according to claim 1 Ru der oil pressure sensor for detecting the oil pressure.   6. The operation prohibiting means according to claim 5, wherein the operation of both the intake side variable valve mechanism and the exhaust side variable valve mechanism is prohibited when the oil pressure detected by the oil pressure sensor is lower than a first oil pressure threshold. A variable valve operating device for an internal combustion engine. Said actuation inhibiting means, claim hydraulic pressure detected by the oil pressure sensor is lower than the second oil pressure threshold value is higher than the first oil pressure threshold value, it prohibits the operation of only one of the variable valve mechanism described above 6 A variable valve operating apparatus for an internal combustion engine according to claim 1. An intake side hydraulic control valve that switches and controls the supply hydraulic pressure from the hydraulic source to the intake side variable valve mechanism, and an exhaust side hydraulic control valve that switches and controls the supply hydraulic pressure from the hydraulic source to the exhaust side variable valve mechanism And having
8. The variable valve operating apparatus for an internal combustion engine according to claim 1, wherein the operation prohibiting unit prohibits the operation of the variable valve operating mechanism by prohibiting the supply of hydraulic pressure by the hydraulic control valve. 9. The variable valve operating apparatus for an internal combustion engine according to claim 1, wherein the one variable valve operating mechanism is an exhaust side variable valve operating mechanism.

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